Noncorrosive acid, solvent and nonionic surfactant composition

ABSTRACT

A cleaning solvent useful in the cleaning of metal surfaces, e.g. nickle-iron alloys, contains sulfamic acid, citric acid, a solvent for hydrocarbon residues, and a surfactant.

AU 165 FX United States Patent [1 1 Alexander et al.

[ NONCORROSWE ACID, SOLVENT AND NoNioNlc SURFACTANT COMPOSITION [75]Inventors: George B. Alexander; Norman F.

Carpenter, both of Tulsa, Okla.

[73] Assignee: The Dow Chemical Company,

Midland. Mich.

221 Filed: Jan. 18,1973

[2i] Appl. No.: 324.651

[52] US. Cl. 252/143; 252/146; 252/DIG. l:

252/87 [51] Int. Cl. Clld 7/50; Cl id 7/08 [58] Field of Search 292/143.146, X70, DIG. l. 292/87 1 Sept. 30, 1975 Primary E.\'aminerBenjamin R.Padgett Assistant Examiner-E. A. Miller Attorney, Agent, or Firm-BruceM. Kanuch 5 7 ABSTRACT A cleaning solvent useful in the cleaning ofmetal surfaces, e.g. nickle-iron alloys, contains sulfamic acid, citricacid, a solvent for hydrocarbon residues, and a surfactant.

6 Claims, No Drawings NONCORROSIVE ACID, SOLVENT AND" NONIONICSURFACTANT COMPOSITION The invention described herein was made in theperformance of work under a NASA contract and is subject to theprovisions of section 305 of the National Aeronautics and Space Act of1958, Public law 85-568 (72 Stat. 435; 42 U. S. C. 2457).

BACKGROUND OF THE INVENTION I The invention relates generally to thecleaning of metal surfaces. More specifically, the invention pertains toa composition useful for the dynamic cleaning of such metals as lnvaralloy, which is a nickel-iron alloy especially suited for cryogenictemperatures because of its low thermal expansivity. A representativesample of this alloy contains the following elements by weight percent:

Iron 61 .4 64.4 Nickel 34.5 36.5 Cobalt 0.50 Titanium 0.30 0.60Manganese 0.30 0.60 Silicon $0.30 Carbon $0.05 Phosphorus 50.015 Sulfur$0.015

Lead 5 0.0l5

Tin $0.015 Selenium $0.010

Cleaning. alloys for use in cryogenic applications, such as piping forextremely low temperature fuel and oxidizer systems in rockets andspacecraft presents difficult problems: for example, the systems must bedevoid of all hydrocarbon and particulate contamination. Conventionalcleaning solvents are not satisfactory for the present purpose.

Although acids such as phosphoric, sulfuric, and hydrochloric displaylow corrosion rates, they produce objectionable smut on the metalsurface. Smut is de- SUMMARY OF THE INVENTION The present compositionproduces minimum corrosive effect while effectively removing hydrocarbonresidue and particulate matter from a metal surface. The composition isan aqueous solution of sulfamic acid, citric acid, a solvent forhydrocarbon residues, e.g., 2- butoxyethanol. and a surfactant. Adynamic cleaning procedure involves flowing this composition over ametal surface to be cleaned at a flow rate and in an amount sufficientto clean the metal surface.

DETAILED DESCRIPTION OF THE INVENTION The composition may be prepared bymixing any or all of the ingredients together and then adding water orby adding the ingredients one at a time to water. All percentageshereafter mentioned are to be taken as weight percentages unlessotherwise indicated. The sulfamic acid should be present in an amountbetween 8 and 12 percent of the aqueous solution, preferably 10%. Thecitric acid should be present in an amount between 4 and 6% of theaqueous solution, preferably 5%.

The solvent for hydrocarbon residues is a substance capable ofdissolving hydrocarbon residues, e.g., greases, waxes or oils, presenton the metal surface or created during the cleaning. Included within ouruse of the term solvent are those substances popularly termeddegreasers, however, the present solvents will in addition dissolvecertain residual organic con-- taminants not properly defined asgreases.

Such solvent must be soluble in and nonreactive with the acid cleaningsolution as well as being capable of ethers such as 2-butoxyethanol.-'

2-methoxyethanol, and Z-ethoxyethanol. The solvent should be present inan amount between 4 and 6% of the aqueous cleaning solution, preferably5%. l

The surfactant serves as a wetting agent, i.e., it lowers the surfacetension of the water, and emulsifics and helps to remove hydrocarbonresidues. Any nonionic surfactant which has a cloud point in excess ofabout F. and which at a concentration of O. 1% in the present acidcleaning solution has a surface tension of about 32 dynes/cm. or less isusable. Cloudpoint is the temperature at which the surfactant becomesinsoluble in the composition. Representative substances include linearalcohol ethoxylates, polyoxyethylene esters, and alkyl aryl polyethyleneoxides. An especially useful surfactant comprises a mixture of primaryalcohols with. 10-12 atoms carbon chains, 60% ethoxylated. Thesurfactant should be present in an amount between 0.095 and 0.15% of theaqueous mixture, preferably 0.1%.

The present composition is useful in cleaning metal surfaces in general.It is particularly useful in the cleaning of iron-nickel alloys, carbonsteel. and titanium.

The composition will satisfactorily clean metal surfaces at ambienttemperatures. At lower temperatures excessive time is required andcleaning is less efficient. Higher temperatures usually ease thecleaning but may cause objectional corrosion rates. Operatingtemperatures within the range of about 50 to F. are feasible for the useof the present cleaning solution; the preferred operating temperaturesare within the range of.

about 70-80F.

It is found that although the present composition is useful in cleaningmetal surfaces in static applications, it is particularly useful indynamic cleaning techniques.

such as cleansing the interior of a pipe by passing the cleaning solventthrough the pipe. In such applications,

it is important to choose an appropriate flow rate. This rate depends onthe pipe size and the degree of cleaning required. Higher flow rates arefound to induce greater turbulence at the metal surface which allows thesolvent to pick up occluded particles. Thus, removal of particulatecontamination to leave only a very small residue will require higherflow rates. For exam- -tioners of this invention to effect the desireddegree of cleaning based on the parameters present. A representativerange of rates is from 2 to about 30 feet per secend; on iron-nickelalloys the preferred rate is 4 feet per second.

The length of time over which the flow is continued depends on theamount of contaminant desired to be removed and the amount of corrosionof the metal surface which is tolerable. Corrosion incurred in turndepends, inter alia, on flow rate. Thus, more complete cleaning andhigher flow rates cause greater corrosion of the-surfaces. Aniron-nickel alloy pipe contaminated with triolein and mineral oil in adensity of from about .04 to about .08 grams per square inch waspreferably cleaned for 2 hours at a cleaning solvent flow rate of 4ft./sec., for 6 hours at 2 ft./sec., and for 0.5 hour at 30 ft./sec.

It is desirable to follow the cleaning flow with a water flush to removeresidual cleaning solution. With some surfaces it is also desirable touse a passivation flush,

utilizing, for example, aqueous solutions of citric acid or sodiumnitrite or a combination of the two. The passivation flush renders themetal surface less susceptible to oxidation thus forming an oxide on thecoating alloy exposed metal surface. For example, a newly cleanediron-nickel alloy was passivated by flowing a 1% citric acid solutionover the surface at 5.5 ft./sec. for 10 min., followed by a flow ofO. 1%aqueous sodium nitrite solution at 5.5 ft./sec. for 10 min. Thereafter,the surface was rinsed with a 20 min. flow of water at a rate of 3.5

ft./sec.

1n the following examples cleaning mixtures comprising variousproportions of ingredients were tested in static and dynamic cleaningapplications.

EXAMPLE l .thus to introduce air into the liquid. The amount of metallost by corrosion and the depth of corrosion penetration were measured,and the cleaning effectiveness was evaluated visually. The results ofthese tests are tabulated in Table l.

all

The iron nickel alloy contained the following in weight percent:

lron 61.4 64.4 Nickel 34.5 36.5 Cobalt 0.50 Titanium 0.30 0.60 Manganese0.30 0.60 Silicon S 0.30 Carbon 0.05 Phosphorus 5 0.015 Sulfur 5 0.015

Lead 5 0.015

Tin 5 0.015 Selenium 5 0.010

TABLE I STATIC CLEANING OF IRON-NICKEL ALLOY COUPONS Metal Loss Wt.'Corrosion Penetration Test No. Cleanliness (mg/dmlhr) (mils/yr) 1 Clean6 2.9 2 17 8.2 3 21 10.0 4 47 23.0 5 Trace 6 2.9 6 4.8 7 12 5.8 8 Minor9 4.3 9 Some 5.1

COMPOSITION Z-butoxy Sulfamic Citric ethanol S" Test No. Weight percentof aqueous solution 1 20 2 20 5 0.1 3 0.1 4 l5 5 0.1 5 l5 0.1 6 10 5 50.1 7 5 0.1 8 5 5 5 0.1 9 l8 2 0.1

'S=A surfactant which is a mixture of primary alcohols of about 10m 12memher carbon chains. about 6054 cthoxylated.

EXAMPLE 2 In this example dynamic cleaning tests were performed on theinterior surface of an iron-nickel alloy pipe. The tests in this examplewere performed on the same iron-nickel alloy used in Example 1,' whichalso had been contaminated with the same substances used in Example l. A12 inch length of 2 inch diameter pipe was subjected to a flow of thepresent cleaning solution. In each test the cleaning solution wasconducted through the pipe at a rate of 5.5 ft./sec. for a period of 2hours. This flow as flowed by a water flush for 0.17 hours at a rate of3.5 ft./sec. The cleaning solution was at a temperature of between 66and 74F. with initial contaminations of varying amounts, the parametersof corrosion metal loss, corrosion penetration depth, and residualhydrocarbon amount were measured and 2 visual evaluation of the cleaningeffectiveness was made. The results are tabulated in Table 11.

TABLE ll DYNAMIC CLEANING OF lRON-NlCKEl. ALLOY PIPE lnitialConcentration mg. (triolein Cleanliness +mineral oil) visual +1.0 m1.Residual observation Metal Loss Corrosion particulate Hydrocarbon smutWeight Penetration Test No. solids (mg) present (mg/dmlhr) (mils/yr.)

l 5300 1.6 Clean 102 49 2 5800 1.7 22 3 4400 1.7 72 5.8

5 TABLE II-Continued DYNAMIC CLEANING OF IRON-NICKEL ALLOY PIPE InitialConcentration mg. (triolein Cleanliness +mineral oil) visual +l .0 ml.Residual observation Metal Loss Corrosion particulate Hydrocarbon smutWeight Penetration Test N0. solids (mg.) present (mg/dmlhr) (mils/yr.)

4 5700 2.0 69 33 5 3300 0.6 rust 20 9.7 6 4 I I .9 22 l l 7 4700 2.6dirty 44 22 COM POSITION Z-hutoxy Sulfamic Citric ethanol Test No.Weight percent of aqueous solution I I0 5 5 ().l

2 l0 5 5 ()fl '5' herein is the same mixture as that defined by S inTable I.

What is claimed is:

l. A composition comprising in percentages by weight the followingingredients:

a. about 8 to 12% sulfamic acid,

b. about 4 to 6% citric acid;

0. about 4 to 6% of a nonionic solvent for hydrocarbon residues whichsolvent is characterized as not producing turbidity at 75F. when presentin said composition,

d. about 0.095 to 0.15% ofa soluble nonionic surfactant which surfactantis characterized as having a cloud point of at least about 90F. andhaving a surface tension of about 32 dynes/cm. or less when present inan amount of 0.1% of said composition, and

e. the balance, water.

2. The composition of claim 1 wherein the nonionic solvent forhydrocarbon residues is a glycol ether.

3. The composition of claim 1 wherein the solvent is chosen from thegroup consisting of 2-butoxyethanol,

2-( 2-butoxyethoxy)ethanol, thanol, Z-methoxyethanol, and2-ethoxyethanol.

4. The composition of claim 1 wherein the soluble nonionic surfactant ischosen from the group consisting of linear alcohol ethoxylates,polyoxyethylene esters,.

and allyl aryl polyethylene oxides.

s. The composition of claim 1 wherein the soluble to about 12 membercarbon chains, about 60% ethoxylated, e. 79.9% water.

2-(2-ethoxyethoxy)e-

1. A COMPOSITION COMPRISING IN PERCENTAGE BY WEIGHT THE FOLLOWINGINGREDIENTS: A. ABOUT 8 TO 12% SULFAMIC ACID, B. ABOUT 4 TO 6% CITRICACID C. ABOUT 4 TO 6% OF A NONIONIC SOLVENT FOR HYDROCARBON RESIDUESWHICH SOLVENT IS CHARACTERIZED AS NOT PRODUCING TURBIDITY AT 75*F. WHENPRESENT IN SAID COMPOSITION, D. ABOUT 0.095 TO 15% OF A SOLUBLE NONIONICSURFACTANT WHICH SURFACTANT IS CHARACTERIZED AS HAVING A CLOUD POINT OFAT LEAST ABOUT 90*F. AND HAVING A SURFACE TENTION OF ABOUT 32 DYNES/CM.OR LESS WHEN PRESENT IN AN AMOUNT OF 0.1% OF SAID COMPOSITION, AND E.THE BALANCE, WATER.
 2. The composition of claim 1 wherein the nonionicsolvent for hydrocarbon residues is a glycol ether.
 3. The compositionof claim 1 wherein the solvent is chosen from the group consisting of2-butoxyethanol, 2-(2-butoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol,2-methoxyethanol, and 2-ethoxyethanol.
 4. The composition of claim 1wherein the soluble nonionic surfactant is chosen from the groupconsisting of linear alcohol ethoxylates, polyoxyethylene esters, andallyl aryl polyethylene oxides.
 5. The composition of claim 1 whereinthe soluble nonionic surfactant is a mixture of primary alcohols ofabout 10 to about 12 member carbon chains, about 60% ethoxylated.
 6. Thecomposition of claim 1 comprising the following proportions: a. 10%sulfamic acid, b. 5% citric acid, c. 5% 2-butoxyethanol, d. 0.1% of amixture of primary alcohols of about 10 to about 12 member carbonchains, about 60% ethoxyLated, e. 79.9% water.